Diagnostic test matrices have revolutionized the health care industry by focusing on relatively easy-to-use devices. For examples, pregnancy-testing dip sticks are commonplace in market facilities throughout the world. Fecal occult monitoring devices, such as the Hemoccult.RTM. brand fecal occult blood test, allow for obtaining samples in the privacy of the patient's home whereby analysis of the sample can be accomplished at a screening facility.
Another form of such test matrices are chromatographic-type assaying systems. Chromatographic-type assaying systems have enjoyed widespread use in the diagnostic fields for several years. Such devices typically rely upon a format whereby a solution comprising a carrier solvent and a test sample suspected of containing an analyte to be detected, is applied to a thin, flat, absorbent medium, which typically has incorporated thereon a binding partner to the analyte. The solution is applied to the absorbent medium and moves along the medium by way of capillary action. A labeling scheme is then utilized to determine the presence of the immobilized analyte. This type of assay is generally referred to as an "immunochromatographic assay". There are two types of immunochromatographic assay types, generally referred to as "sandwich", or "capture", immunochromatographic assays, and "competitive" immunochromatographic assays.
Sandwich immunochromatographic assays typically involve mixing a sample containing an analyte of interest with either a monoclonal or polyclonal "capture" antibody to the analyte (alternatively, the sample can be added directly to a chromatographic medium having affixed thereto the capture antibody). The antibody can be conjugated to some form of label, for example, colored latex beads, chemiluminescent, enzymatic, fluorescent, radioactive, colloidal gold, etc. Thereafter, an analyte-labeled antibody complex is formed. This complex is then applied to the chromatographic medium which has a second monoclonal antibody or additional polyclonal antibodies immobilized thereon. As the complex moves along the medium, the analyte-labeled antibody complex becomes bound to the immobilized antibody, forming an immobilized antibody-analyte-labeled antibody complex. The label can then be read to provide an indication of the presence (and quantity) of the analyte in the sample medium.
Competitive immunochromatographic assays typically involve mixing a sample containing an analyte of interest with a known quantity of the same analyte having a label conjugated thereto. This mixture is then added to a known quantity of immobilized antibody to the analyte. As the mixture moves along the medium, a competition is created between the sample-analyte and the labeled-analyte: the more sample-analyte available for binding to the immobilized antibody, the less label that will be detected. Thus, the amount of sample-analyte is inversely proportional to the amount of label obtained.
Immunochromatographic assays are not without drawbacks. For example, with respect to, e.g., fecal samples, mucous-based samples, throat or vaginal swabs, etc., it is very difficult to apply these materials to the chromatographic medium directly. Thus, these materials are usually applied to the chromatographic medium, whereupon a solvent solution is added thereto, the solvent being capable of carrying the analyte of interest to a particular location on the chromatographic medium. Problems arise using this approach because the materials can clog the pores of the chromatographic medium, making chromatographic analysis extremely difficult because of interference with the flow of the solvent caused by such clogging. Additionally, these materials can include therein extraneous matter which can interfere with the analysis due to, e.g., non-specific binding with the analyte antibodies, or interference with the particular label utilized for the analyses.
An alternative to this approach is to utilize extraction or pretreatment reactions whereby the sample material is added to a liquid extracting medium such that the sample is brought from its solid or semi-solid form to a liquid form. Conventionally, this is accomplished by a technician in a laboratory setting and is carried out in small transfer vessels, whereby the extraction medium containing the sample is added to the chromatographic medium via, e.g., a pipette. This scenario raises additional problems, particularly in the areas of contamination and waste disposal. Such problems are particularly relevant with respect to the possibility of transfer of communicable diseases to the technician(s), as well as the potential for cross-contamination of samples.
What is needed, in view of the foregoing, is a device that will readily facilitate the extraction of an analyte from a sample for analysis of material in the sample, and that ensures that contamination and waste byproducts are substantially minimized.